Poly-α-olefins (PAOs) are used in the industry as base stocks for functional fluids, such as lubricants and transmission fluids. PAOs have conventionally been prepared by polymerization of α-olefins using a Friedel-Crafts catalyst, such as BF3 or AlCl3. PAOs have also been prepared by supported, reduced chromium catalysts, Ziegler-Natta or metallocene catalysts. The polymer product typically contains one terminal unsaturation per polymer chain. PAOs typically are then hydrogenated to stabilize the polymer against oxidation and degradation.
A drawback in using PAOs is their lack of compatibility with common polar additives, such as antioxidants, anti-rust agents and anti-wear agents. Conventionally, expensive polar organic esters have been added to PAO lubricants to render them compatible. Useful commercial formulations may contain 20% or more of such esters to achieve a fully homogeneous lubricant blend. Examples of such esters include, for example, bis-tridecanol adipate and pentaerythritol hexanoate. Due to the expense of such esters, it would desirable to eliminate the need for them.
Commercial PAO production processes commonly generate a distillate byproduct that has the following: (I) contains mostly C8H16 to C30H60 oligomers (average C20H40), (II) exhibits a relatively low average molecular weight, typically about 280, and (III) contains terminal olefin in the amount of at least about 25%. The distillate byproduct, which may amount to several percent of total PAO production, has little value at present. Thus, there is a need in the industry to develop a valuable use for the PAO distillate byproduct.
Alkylated diarylamines, such as alkylated diphenylamines, are known to be effective as stabilizers and/or antioxidants in a wide variety of organic materials, such as mineral oil-derived lubricants and synthetic lubricants.
It would be desirable to have a PAO product that could be synthesized from the distillate by product. It would be desirable to have a PAO product in which polar additives are soluble or miscible.